Impacto de la dieta sobre la inducción de infección con quistes de Giardia lamblia en ratas Sprague-Dawley / Impact of diet on the induction of infection with Giardia lamblia cysts in Sprague-Dawley rats

OBJECTIVE: To assess the effect of malnutrition on the development of giardiasis in Sprague-Dawley rats, using different inoculum sizes of Giardia lamblia cysts. MATERIAL AND METHODS: An experimental study was conducted between 1995 and 1999 at Centro de Investigación, Alimentación y Desarrollo (Center for Research, Food, and Development), in Hermosillo, Sonora, Mexico. The study population consisted of two groups of six to eight experimental units that were fed two different diets and inoculated five different concentrations of Giardia lamblia cysts. Data were collected on excretion of cysts, weight gain, food intake, bowel contents, and macro and microscopic lesions in the intestinal mucosa. Statistical analysis consisted of analysis of variance and residuals. RESULTS: Animals fed with a diet meeting nutritional requirements required an infecting inoculum of 60 cysts, while malnourished rats required only six cysts to develop mucosal lesions. CONCLUSIONS: Weight gain monitored during ten days was not a good indicator of Giardia lamblia infection. Infection depended on cyst inoculum size as well as on the nutritional status of the tested animals.

Influence of dietary protein on DDT-induced immune responsiveness in rats.

The influence of protein deficiency was evaluated on immune responsiveness after subchronic DDT exposure in albino rats. Rats were given 20%, 12% and 3% protein diets and exposed to DDT (20, 50 or 100 ppm) for 4 weeks. DDT (50 and 100 ppm) induced humoral and cellular immune suppression only in rats fed on 3% protein diet. There was (a) an increase in the albumin/globulin ratio, (b) suppression in IgM and IgG levels, and (c) attenuation in the tetanus toxoid-induced antibody responses. Further, in rats immunized with tetanus toxoid, the leucocyte and macrophage migration inhibition were also attenuated. Moreover, these animals maintained on 3% protein diet showed depression in humoral and cellular immune responses to antigen in a dose-dependent pattern after exposure to DDT at dose levels which were not immunosuppressive for rats on 12% or 20% protein diet. These results suggest that dietary protein content may predispose to the immunotoxic effects of DDT exposure, and also be a crucial determinant in DDT detoxification.

Effects of protein deficiency and natural intestinal infection with Giardia lamblia on jejunal intraepithelial lymphocytes in rats of different ages

1. The interaction between experimental protein deprivation and natural intestinal infection by Giardia lamblia was studied in terms of its effects on the intraepithelial lymphocyte (IEL) population and morphology of the jejunal mucosa of rats of different ages. 2. Young, adult and old male Wistar rats received a protein-deficient diet (2 casein) or a control diet (20 casein) for 42 days. Mucosal height and the number of lymphocytes located among 500 consecutive epithelial cells (EC) along the villi or crossing the basement membrane were determined in PAS-stained jejunal fragments. 3. The number of IEL increased progressively with animal age, from 14 to 25 per 100 epithelial cells, with significant differences between age ranges. However, the number of IEL did not differ between control and protein-deficient rats in any of the age groups. The proportion of lymphocytes crossing the basement membrane was approximately two-fold greater in young (2.8/100 EC) and adult (5.8/100 EC) protein-deficient animals than in their respective controls (1.6 and 2.8/100 EC). The intensity of parasite colonization was moderate, from 3 to 5/100 EC and did not differ between groups. The pattern of morphologic changes of jejunal mucosa in protozoal infection did not differ between control and protein-deficient animals in any of the three age groups. 4. We conclude that intestinal infection with Giardia lamblia probably stimulated the local immune response, masking the reduction of the IEL population induced by protein deficiency. The increase in lymphocyte numbers with age may be related to prolonged antigenic stimulation promoted by infection.

Immunological effects of amino acid deficiency and zinc overloading in rats

The dual effect of amino acid deficiency and zinc hypersupplementation upon both cell mediated and humoral immune responses was studied in male albino Sprague Dawely rats. Results indicated that phytohaemagglutinin [PHA] and poke weed mitogenic response [PWM], in rats fed deficient amino acid [a.a.] and normal zinc [Zn] diet, was significantly decreased. However, upon Zn supplementation, no significant change could be observed in either PHA or PWM. On the other hand, haemagglutinin as well as plaque forming cells [PFC] were diminished in rats fed deficient a.a. and normal Zn. Hyperapplication of Zn in the diet provided a marked decrease in PFC but had no effect upon haemagglutinin. The prominent outcome of this study is that the immune response whether cell-mediated or humoral does not appear to be substantially influenced by dietary amino acid type but by its deficiency in the diet. It can also be concluded that Zn alone has failed in treating the impairment of humoral immune response, caused by amino acid deficiency; and that Zn and amino acids play an important role in the alteration of the immune response due to heir interindependent relationship